For this case, the first thing to do is subtract both values.
We have then:
Joanie's bag of trail mix = 0.75 kilogram
She and some friends eat = 0.5 kilogram
Subtracting we have:
0.75 - 0.5 = 0.25 Kilogram
number line all:
0 --- 0.25 --- 0.5 --- 0.75
number line when they ate trail mix:
/ 0 / --- /0.25/ --- /0.5/ --- 0.75
Remaining amount
0.25 kilograms
Answer:
0.25 kilograms of trail mix are left
